1. Field of the Invention
The present invention relates generally to a toothbrush having needle-shaped bristle, and in particular, to a toothbrush tufted with 13 to 18 mm long needle-shaped bristles tapered only on one end, and a manufacturing method thereof.
2. Description of the Related Art
Since the introduction of a toothbrush tufted with tapered bristles for effective plaque removal and prevention of damage to gums during teeth brushing, its verified effectiveness has recently made this toothbrush popular.
For fabrication of such a traditional toothbrush, 28 to 33 mm long bristles, which are needle-shaped on one end t and non-needle-shaped on the other end n, are folded over such that the needle-shaped portion is longer than the non-needle-shaped portion, as illustrated in FIGS. 1A and 1B. The folded portions are picked up by means of a cut wire and fixedly inserted into fixing holes in the head of the toothbrush. The toothbrush manufacturing method is disclosed in Japanese Patent Open-Laid No. Sho 61-10495.
As illustrated in FIG. 2, another traditional toothbrush is made by folding needle-shaped bristles, which are 28 to 33 mm long and tapered 4 to 8 mm on both ends, in two equal halves and planting them in the above-described manner. This toothbrush manufacturing technique is disclosed in Japanese Patent Open-Laid No. Hei 5-15834.
In Korea Patent No. 311360, the present inventor disclosed a toothbrush tufted with ordinary bristles tapered on both ends and at least one 1 to 10 mm longer bristle 62 of the same shape.
The above techniques, though they have their own benefits and drawbacks, commonly boast excellent plaque removal and improved health of gums.
However, they suffer from the same shortcomings of complex manufacturing, high inferior goods rate, and thus high production cost, for the following reasons.
(1) In order to shape ordinary polyester bristles into needles, the tips of the bristles are treated with a chemical such as caustic soda or sulphuric acid. During this process, the total length and tapered length of the bristles are difficult to control, thereby resulting in many inferior bristles. (2) In the case of a today's popular needle-shaped toothbrush tufted with bristles tapered on both ends, both tips of the bristles are treated in the above-described manner, for needle shaping. Even if one tip of a bristle is successfully tapered, the failure of the other tip leads to the whole failure of the bristle. (3) There are no appropriate applications for utilizing bristles having wrong lengths.
Besides, the traditional toothbrush bristles are planted in simple patterns and not tightly fixed, as illustrated in FIG. 4. As a result, the bristles often fall out of the brushes. The cause is identified that the bristles are folded by half, picked up with a wire, and pushed into fixing holes 10 by inserting the wire itself.